Re: [PATCH v2] thermal: re-calculate k_po/k_pu when update sustainable power
From: Daniel Thompson
Date: Tue Jan 05 2016 - 13:03:07 EST
On 05/01/16 17:40, Punit Agrawal wrote:
Daniel Thompson <daniel.thompson@xxxxxxxxxx> writes:
On 05/01/16 16:33, Javi Merino wrote:
On Mon, Jan 04, 2016 at 11:22:26AM +0000, Daniel Thompson wrote:
On 01/01/16 00:03, Leo Yan wrote:
Hi Eduardo,
Thanks for review.
On Thu, Dec 31, 2015 at 09:21:26AM -0800, Eduardo Valentin wrote:
On Wed, Dec 30, 2015 at 06:38:40PM +0800, Leo Yan wrote:
k_po/k_pu are in essence ratio values compared with sustainable power.
So when update sustainable power, we can recalculate k_po/k_pu simply
with below formula:
sustainable_power(new)
k_p(new) = ---------------------- * k_p(old)
sustainable_power(old)
Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
---
drivers/thermal/thermal_core.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index d9e525c..223f8df 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -908,7 +908,7 @@ sustainable_power_store(struct device *dev, struct device_attribute *devattr,
const char *buf, size_t count)
{
struct thermal_zone_device *tz = to_thermal_zone(dev);
- u32 sustainable_power;
+ u32 sustainable_power, old_val;
if (!tz->tzp)
return -EIO;
@@ -916,8 +916,12 @@ sustainable_power_store(struct device *dev, struct device_attribute *devattr,
if (kstrtou32(buf, 10, &sustainable_power))
return -EINVAL;
+ old_val = tz->tzp->sustainable_power;
+
tz->tzp->sustainable_power = sustainable_power;
+ tz->tzp->k_po = (tz->tzp->k_po * sustainable_power) / old_val;
+ tz->tzp->k_pu = (tz->tzp->k_pu * sustainable_power) / old_val;
I believe this has to be done by the governor. These properties are
power_allocator specific. thermal_core should not really care about
them.
Okay, I will try to update these properties in power_allocator.c.
Javi, do you think this is fine for you?
If sustainable power were to change frequently (perhaps on
entry/exit of a fan inhibitor mode?) then we would accumulate
rounding errors here...
Can you elaborate on the use case? What is this fan inhibitor mode?
It's made up.
I was trying to think of use cases which might result in the userspace
wishing to make frequent changes the maximum sustainable power. For
designs where the system remains thermally overcommited even with the
fan running then having a mode where the fan must not spin up would
require such a change.
If there isn't an immediate use case, we should hold off making any
changes until they're really needed.
Fair point but do note that the fan inhibition comments were used to
illustrate a bug in the patch. They were not an argument for (or
against) the value of patch itself.
Daniel.
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